Sort algorithm Four: Quick sort (Quicksort)

Quick Sort (Quicksort), because of its fast sort of name, although TA's average time complexity is O (nlgn), but from the subsequent simulation results, TA is faster than merge sorting and heap sorting.

The idea of division and treatment is also used in quick sorting.

(i) Algorithm implementation

1 protected voidQuicksortint[] Array,intFirstintLast ) {2 3         intPivot =Array[first];4         inti =First ;5         intj = last-1;6         BooleanSerachbig =true;7          while(I <j) {8             if(serachbig) {9                 if(Array[j] <pivot) {TenArray[i] =Array[j]; Onei++; ASerachbig =false; -}Else { -j--; the                 } -}Else { -                 if(Array[i] >pivot) { -ARRAY[J] =Array[i]; +j--; -Serachbig =true; +}Else { Ai++; at                 } -             } -         } -Array[i] =pivot; -  -         if(I-first > 1) { in quicksort (array, first, i); -         } to         if(Last-i > 2) { +Quicksort (Array, i + 1, last); -         } the}

Quicksort

1) The average time complexity of fast sequencing is also O (NLGN)

2) Quick Sort is in-situ sort

(ii) Simulation results

**************************************************
Number to Sort is:2500
Array to sort is:{378132,303655,213274,506865,348563,122685,857064,624884,376943,281167 ...}
Cost time of "QuickSort" is (milliseconds): 0
Sort result of "QuickSort": {93,862,991,1285,2737,2938,3119,3372,3933,4647 ...}
**************************************************
Number to Sort is:25000
Array to sort is:{737677,533972,6498,772664,516805,635063,278963,284929,577222,593745 ...}
Cost time of "QuickSort" is (milliseconds): 2
Sort result of "QuickSort": {1,247,270,375,386,428,431,515,588,623 ...}
**************************************************
Number to Sort is:250000
Array to sort is:{481818,650680,957183,733420,611440,739781,495686,560166,942993,492550 ...}
Cost time of "QuickSort" is (milliseconds): 23
Sort result of "QuickSort": {0,6,10,17,20,22,23,26,32,37 ...}

Related code:

1  PackageCom.cnblogs.riyueshiwang.sort;2 3 Importjava.util.Arrays;4 5  Public classQuickSortextendsAbstractsort {6 7 @Override8     protected voidSortint[] tosort) {9Quicksort (tosort, 0, tosort.length);Ten     } One  A     protected voidQuicksortint[] Array,intFirstintLast ) { -  -         intPivot =Array[first]; the         inti =First ; -         intj = last-1; -         BooleanSerachbig =true; -          while(I <j) { +             if(serachbig) { -                 if(Array[j] <pivot) { +Array[i] =Array[j]; Ai++; atSerachbig =false; -}Else { -j--; -                 } -}Else { -                 if(Array[i] >pivot) { inARRAY[J] =Array[i]; -j--; toSerachbig =true; +}Else { -i++; the                 } *             } $         }Panax NotoginsengArray[i] =pivot; -  the         if(I-first > 1) { + quicksort (array, first, i); A         } the         if(Last-i > 2) { +Quicksort (Array, i + 1, last); -         } $     } $  -      Public Static voidMain (string[] args) { -          for(intj = 0, n = 2500; J < 3; j + +, n = n * 10) { the System.out -. println ("**************************************************");WuyiSystem.out.println ("Number to Sort is:" +n); the             int[] array = Commonutils.getrandomintarray (n, 1000000); -System.out.print ("Array to sort is:"); Wu Commonutils.printintarray (array); -  About             int[] Array1 =arrays.copyof (array, n); $             NewQuickSort (). Sortandprint (array1); -         } -     } -  A}

Quicksort.java

Sort algorithm Four: Quick sort (Quicksort)